1. Field of the Invention
The present invention relates generally to GNSS applications, including vehicle guidance and navigation.
2. Description of the Related Art
The use of a Global Navigation Satellite System (GNSS) for guidance, navigation and machine control has significantly advanced these fields and enabled a number of applications, including many in agriculture, transportation and other industries. GNSS systems include the Global Positioning System (GPS) and other satellite-based systems. Various GNSS receivers are available for aviation, marine and terrestrial vehicles. The GNSS information provided by such receivers can be processed and used for navigation. In more sophisticated systems, vehicle guidance can be automatically controlled using such information. For example, a predetermined travel or flight path can be programmed into an on-board computer. The vehicle guidance system can automatically maintain appropriate course parameters, such as course, heading, speed, altitude, etc. Control system, feedback theory and signal filtering techniques can be used to interactively anticipate (with higher order systems) and compensate for course deviations and navigation errors. Such sophisticated autopilot and automatic steering systems tend to involve powerful computers and complex flight and steering controls integrated with manual controls.
Accurate vehicle and equipment guidance is an important objective in agriculture. For example, cultivating, tilling, planting, spraying, fertilizing, harvesting and other farming operations typically involve specialized equipment and materials, which are operated and applied by making multiple passes over cultivated fields. Ideally, the equipment is guided through accurately-spaced passes or swaths, the spacing of which is determined by the swath width of the equipment. Gaps and overlaps can occur when operators deviate from the ideal guide paths, resulting in under-coverage and over-coverage respectively. Such gaps and overlaps are detrimental to agricultural operations and can reduce crop yields. For example, gaps in coverage reduce the effective areas of fields being cultivated and treated. Overall crop production may suffer as a result. Overlaps in coverage tend to be inefficient and wasteful of materials, such as fuel, fertilizer, pesticides, herbicides, seed, etc. Another potential problem with overlapping coverage relates to the potentially crop-damaging effects of double applications of certain agricultural chemicals.
Previous mechanical systems for assisting with the guidance of agricultural equipment include foam markers, which deposit foam along the swath edges. The foam lines produced by foam markers provide operators with visible reference lines on which subsequent passes can be aligned. However, foam marking systems consume foam-making materials and provide only temporary foam marks. Moreover, guiding along such foam lines requires the operators to visually estimate the locations of the implement ends relative to the foam lines. Implements such as spray booms with effective widths of more than 50 feet are in common use, thus increasing the difficulties associated with visually aligning distant, elevated boom ends with foam lines on the ground.
GNSS technology advanced the field of agricultural guidance by enabling reliable, accurate systems, which are relatively easy to use. GNSS guidance systems are adapted for displaying directional guidance information to assist operators with manually steering the vehicles. For example, the OUTBACK S™ steering guidance system, which is available from Hemisphere GPS LLC of Hiawatha, Kans. and is covered by U.S. Pat. No. 6,539,303 and No. 6,711,501, which are incorporated herein by reference, includes an on-board computer capable of storing various straight-line and curved (“contour”) patterns. An advantage of this system is its ability to retain field-specific cultivating, planting, spraying, fertilizing, harvesting and other patterns in memory. This feature enables operators to accurately retrace such patterns. Another advantage relates to the ability to interrupt operations for subsequent resumption by referring to system-generated logs of previously treated areas.
The OUTBACK S™ GNSS guidance system provides the equipment operators with real-time visual indications of heading error with a steering guide display and crosstrack error with a current position display. They respectively provide steering correction information and an indication of the equipment position relative to a predetermined course. Operators can accurately drive patterns in various weather and light conditions, including nighttime, by concentrating primarily on such visual displays. Significant improvements in steering accuracy and complete field coverage are possible with this system.
Another type of GNSS vehicle guidance equipment automatically steers the vehicle along all or part of its travel path and can also control an agricultural procedure or operation, such as spraying, planting, tilling, harvesting, etc. Examples of such equipment are shown in U.S. Pat. No. 7,142,956, which is incorporated herein by reference. U.S. Patent Application Publication No. 2004/0186644 shows satellite-based vehicle guidance control in straight and contour modes, and is also incorporated herein by reference.
GNSS guidance systems and equipment are distinguished by their vehicle path configuration capabilities. Initially, straight-line AB (i.e. between points A and B) guidance consisted of multiple, parallel straight lines, which were separated by the swath widths of the vehicles. Straight line AB guidance is ideally suited for rectangular fields and continuously-repeating, parallel swathing.
Non-rectangular and terraced fields typically require curvilinear vehicle paths that follow the field perimeters and the terraced elevation contours. Contour guidance systems and methods were developed to accommodate such field conditions using GNSS coordinates to define curvilinear vehicle paths. See, for example, Korver U.S. Pat. No. 5,928,309. GNSS positions can be logged on-the-fly at intervals of, for example, 0.20 seconds. Contour guidance can be accomplished by computer-generating each subsequent pass from the GNSS-defined previous pass and a user-entered swath width.
Another type of GNSS contour guidance equipment outputs guidance signals relative to the edges of all previously logged swaths. Such logged swaths typically correspond to field areas where operations, e.g. spraying, have already been carried out.
A disadvantage with some of the previous GNSS guidance techniques relates to cumulative error propagation, which can result from machine or operator bias towards one side or the other of the vehicle path, or sloping terrain, which can reduce the effective width (as determined in a horizontal plane) of the implement. Significant cumulative guidance errors in the form of overlaps and skips can result from such biases being repeated over an entire field. Another disadvantage with some of the prior art guidance systems relates to their relatively heavy computer processing overhead demands. Multi-tasking guidance and other automated features, such as steering, tended to require relatively powerful on-board computers programmed with sophisticated software and equipped with large capacity memory devices, all of which tended to increase costs and complexity. Accordingly, an objective in automated vehicle guidance is to minimize the use of computer overhead, e.g. by actively guiding to a relatively small subset of the entire logged GNSS position database.
An objective in agricultural guidance is to accommodate both straight-line and contour field conditions. Another objective is to optimize track patterns to accommodate complex field configurations and terracing conditions whereby consistent swathing coverage can be achieved with minimum travel time and distance. Another objective is to accommodate sloping terrain with appropriate adjustments “on-the-fly”. Still further, the system should be adapted for “desktop” preplanning and saving vehicle track patterns covering multiple fields for consistent coverage and repeatability. Automatic steering should be accommodated for “hands-off” operation, taking into account vehicle operating parameters, such as turning radii, speeds, swath widths, etc. Appropriate machine control functions, such as implement steering and spray boom control, should be accommodated.
Heretofore there has not been available a GNSS guidance and control system and method with the advantages and features of the present invention.